Merge branch '1.0-dev' into migration

Author: sokoliva

.release-please-manifest.json

@@ -1 +1 @@
-{".":"1.0.0-alpha.2"}
+{".":"1.0.0-alpha.3"}

CHANGELOG.md

@@ -1,5 +1,12 @@
 # Changelog
 
+## [1.0.0-alpha.3](https://github.com/a2aproject/a2a-python/compare/v1.0.0-alpha.2...v1.0.0-alpha.3) (2026-04-17)
+
+
+### Bug Fixes
+
+* update `with_a2a_extensions` to append instead of overwriting ([#985](https://github.com/a2aproject/a2a-python/issues/985)) ([e1d0e7a](https://github.com/a2aproject/a2a-python/commit/e1d0e7a72e2b9633be0b76c952f6c2e6fe11e3e5))
+
 ## [1.0.0-alpha.2](https://github.com/a2aproject/a2a-python/compare/v1.0.0-alpha.1...v1.0.0-alpha.2) (2026-04-17)
 
 

src/a2a/client/service_parameters.py

@@ -1,7 +1,10 @@
 from collections.abc import Callable
 from typing import TypeAlias
 
-from a2a.extensions.common import HTTP_EXTENSION_HEADER
+from a2a.extensions.common import (
+    HTTP_EXTENSION_HEADER,
+    get_requested_extensions,
+)
 
 
 ServiceParameters: TypeAlias = dict[str, str]
@@ -44,17 +47,18 @@ def create_from(
 
 
 def with_a2a_extensions(extensions: list[str]) -> ServiceParametersUpdate:
-    """Create a ServiceParametersUpdate that adds A2A extensions.
+    """Create a ServiceParametersUpdate that merges A2A extension URIs.
 
-    Args:
-        extensions: List of extension strings.
-
-    Returns:
-        A function that updates ServiceParameters with the extensions header.
+    Unions the supplied URIs with any already present in the A2A-Extensions
+    parameter, deduplicating and emitting them in sorted order. Repeated
+    calls accumulate rather than overwrite.
     """
 
     def update(parameters: ServiceParameters) -> None:
-        if extensions:
-            parameters[HTTP_EXTENSION_HEADER] = ','.join(extensions)
+        if not extensions:
+            return
+        existing = parameters.get(HTTP_EXTENSION_HEADER, '')
+        merged = sorted(get_requested_extensions([existing, *extensions]))
+        parameters[HTTP_EXTENSION_HEADER] = ','.join(merged)
 
     return update

src/a2a/server/request_handlers/default_request_handler_v2.py

@@ -271,11 +271,17 @@ async def on_message_send(  # noqa: D102
             ):
                 self._validate_task_id_match(task_id, event.id)
                 result = event
+                # DO break here as it's "return_immediately".
+                # AgentExecutor will continue to run in the background.
                 break
 
             if isinstance(event, Message):
                 result = event
-                break
+                # Do NOT break here as Message is supposed to be the only
+                # event in "Message-only" interaction.
+                # ActiveTask consumer (see active_task.py) validates the event
+                # stream and raises InvalidAgentResponseError if more events are
+                # pushed after a Message.
 
         if result is None:
             logger.debug('Missing result for task %s', request_context.task_id)
@@ -311,15 +317,18 @@ async def on_message_send_stream(  # noqa: D102
             request=request_context,
             include_initial_task=False,
         ):
+            # Do NOT break here as we rely on AgentExecutor to yield control.
+            # ActiveTask consumer (see active_task.py) validates the event
+            # stream and raises InvalidAgentResponseError on misbehaving agents:
+            #   - an event after a Message
+            #   - Message after entering task mode
+            #   - an event after a terminal state
             if isinstance(event, Task):
                 self._validate_task_id_match(task_id, event.id)
                 yield apply_history_length(event, params.configuration)
             else:
                 yield event
 
-            if isinstance(event, Message):
-                break
-
     @validate_request_params
     @validate(
         lambda self: self._agent_card.capabilities.push_notifications,

tests/client/test_service_parameters.py

@@ -0,0 +1,53 @@
+"""Tests for a2a.client.service_parameters module."""
+
+from a2a.client.service_parameters import (
+    ServiceParametersFactory,
+    with_a2a_extensions,
+)
+from a2a.extensions.common import HTTP_EXTENSION_HEADER
+
+
+def test_with_a2a_extensions_merges_dedupes_and_sorts():
+    """Repeated calls accumulate; duplicates collapse; output is sorted."""
+    parameters = ServiceParametersFactory.create(
+        [
+            with_a2a_extensions(['ext-c', 'ext-a']),
+            with_a2a_extensions(['ext-b', 'ext-a']),
+        ]
+    )
+
+    assert parameters[HTTP_EXTENSION_HEADER] == 'ext-a,ext-b,ext-c'
+
+
+def test_with_a2a_extensions_merges_existing_header_value():
+    """Pre-existing comma-separated header values are parsed and merged."""
+    parameters = ServiceParametersFactory.create_from(
+        {HTTP_EXTENSION_HEADER: 'ext-a, ext-b'},
+        [with_a2a_extensions(['ext-c'])],
+    )
+
+    assert parameters[HTTP_EXTENSION_HEADER] == 'ext-a,ext-b,ext-c'
+
+
+def test_with_a2a_extensions_empty_is_noop():
+    """An empty extensions list leaves the header untouched / absent."""
+    parameters = ServiceParametersFactory.create(
+        [
+            with_a2a_extensions(['ext-a']),
+            with_a2a_extensions([]),
+        ]
+    )
+
+    assert parameters[HTTP_EXTENSION_HEADER] == 'ext-a'
+    assert HTTP_EXTENSION_HEADER not in ServiceParametersFactory.create(
+        [with_a2a_extensions([])]
+    )
+
+
+def test_with_a2a_extensions_normalizes_input_strings():
+    """Input strings are split on commas and stripped, like header values."""
+    parameters = ServiceParametersFactory.create(
+        [with_a2a_extensions(['ext-a, ext-b', '  ext-c  '])]
+    )
+
+    assert parameters[HTTP_EXTENSION_HEADER] == 'ext-a,ext-b,ext-c'

tests/server/request_handlers/test_default_request_handler_v2.py

@@ -28,6 +28,7 @@
 )
 from a2a.types import (
     InternalError,
+    InvalidAgentResponseError,
     InvalidParamsError,
     TaskNotFoundError,
     PushNotificationNotSupportedError,
@@ -1244,3 +1245,169 @@ async def test_on_message_send_with_push_notification():
     push_store.set_info.assert_awaited_once_with(
         result.id, push_config, context
     )
+
+
+class MultipleMessagesAgentExecutor(AgentExecutor):
+    """Misbehaving agent that yields more than one Message."""
+
+    async def execute(self, context: RequestContext, event_queue: EventQueue):
+        await event_queue.enqueue_event(
+            new_text_message('first', role=Role.ROLE_AGENT)
+        )
+        await event_queue.enqueue_event(
+            new_text_message('second', role=Role.ROLE_AGENT)
+        )
+
+    async def cancel(self, context: RequestContext, event_queue: EventQueue):
+        pass
+
+
+class MessageAfterTaskEventAgentExecutor(AgentExecutor):
+    """Misbehaving agent that yields a task-mode event then a Message."""
+
+    async def execute(self, context: RequestContext, event_queue: EventQueue):
+        task = new_task_from_user_message(context.message)
+        await event_queue.enqueue_event(task)
+        updater = TaskUpdater(event_queue, task.id, task.context_id)
+        await updater.update_status(TaskState.TASK_STATE_WORKING)
+        await event_queue.enqueue_event(
+            new_text_message('stray message', role=Role.ROLE_AGENT)
+        )
+
+    async def cancel(self, context: RequestContext, event_queue: EventQueue):
+        pass
+
+
+class TaskEventAfterMessageAgentExecutor(AgentExecutor):
+    """Misbehaving agent that yields a Message and then a task-mode event."""
+
+    async def execute(self, context: RequestContext, event_queue: EventQueue):
+        await event_queue.enqueue_event(
+            new_text_message('only message', role=Role.ROLE_AGENT)
+        )
+        await event_queue.enqueue_event(
+            TaskStatusUpdateEvent(
+                task_id=str(context.task_id or ''),
+                context_id=str(context.context_id or ''),
+                status=TaskStatus(state=TaskState.TASK_STATE_WORKING),
+            )
+        )
+
+    async def cancel(self, context: RequestContext, event_queue: EventQueue):
+        pass
+
+
+class EventAfterTerminalStateAgentExecutor(AgentExecutor):
+    """Misbehaving agent that yields an event after reaching a terminal state."""
+
+    async def execute(self, context: RequestContext, event_queue: EventQueue):
+        task = new_task_from_user_message(context.message)
+        await event_queue.enqueue_event(task)
+        updater = TaskUpdater(event_queue, task.id, task.context_id)
+        await updater.complete()
+        await event_queue.enqueue_event(
+            new_text_message('after terminal', role=Role.ROLE_AGENT)
+        )
+
+    async def cancel(self, context: RequestContext, event_queue: EventQueue):
+        pass
+
+
+@pytest.mark.asyncio
+@pytest.mark.timeout(1)
+async def test_on_message_send_stream_rejects_multiple_messages():
+    """Stream surfaces InvalidAgentResponseError when the agent yields a
+    second Message after the first one (see comment in on_message_send_stream)."""
+    request_handler = DefaultRequestHandlerV2(
+        agent_executor=MultipleMessagesAgentExecutor(),
+        task_store=InMemoryTaskStore(),
+        agent_card=create_default_agent_card(),
+    )
+    params = SendMessageRequest(
+        message=Message(
+            role=Role.ROLE_USER,
+            message_id='msg_multi_stream',
+            parts=[Part(text='Hi')],
+        )
+    )
+    with pytest.raises(InvalidAgentResponseError, match='Multiple Message'):
+        async for _ in request_handler.on_message_send_stream(
+            params, create_server_call_context()
+        ):
+            pass
+
+
+@pytest.mark.asyncio
+@pytest.mark.timeout(1)
+async def test_on_message_send_stream_rejects_message_after_task_event():
+    """Stream surfaces InvalidAgentResponseError when the agent yields a
+    Message after entering task mode (see comment in on_message_send_stream)."""
+    request_handler = DefaultRequestHandlerV2(
+        agent_executor=MessageAfterTaskEventAgentExecutor(),
+        task_store=InMemoryTaskStore(),
+        agent_card=create_default_agent_card(),
+    )
+    params = SendMessageRequest(
+        message=Message(
+            role=Role.ROLE_USER,
+            message_id='msg_after_task_stream',
+            parts=[Part(text='Hi')],
+        )
+    )
+    with pytest.raises(
+        InvalidAgentResponseError, match='Message object in task mode'
+    ):
+        async for _ in request_handler.on_message_send_stream(
+            params, create_server_call_context()
+        ):
+            pass
+
+
+@pytest.mark.asyncio
+@pytest.mark.timeout(1)
+async def test_on_message_send_stream_rejects_task_event_after_message():
+    """Stream surfaces InvalidAgentResponseError when the agent yields a
+    task-mode event after a Message (see comment in on_message_send_stream)."""
+    request_handler = DefaultRequestHandlerV2(
+        agent_executor=TaskEventAfterMessageAgentExecutor(),
+        task_store=InMemoryTaskStore(),
+        agent_card=create_default_agent_card(),
+    )
+    params = SendMessageRequest(
+        message=Message(
+            role=Role.ROLE_USER,
+            message_id='msg_then_task_stream',
+            parts=[Part(text='Hi')],
+        )
+    )
+    with pytest.raises(InvalidAgentResponseError, match='in message mode'):
+        async for _ in request_handler.on_message_send_stream(
+            params, create_server_call_context()
+        ):
+            pass
+
+
+@pytest.mark.asyncio
+@pytest.mark.timeout(1)
+async def test_on_message_send_stream_rejects_event_after_terminal_state():
+    """Stream surfaces InvalidAgentResponseError when the agent yields an event
+    after reaching a terminal state (see comment in on_message_send_stream)."""
+    request_handler = DefaultRequestHandlerV2(
+        agent_executor=EventAfterTerminalStateAgentExecutor(),
+        task_store=InMemoryTaskStore(),
+        agent_card=create_default_agent_card(),
+    )
+    params = SendMessageRequest(
+        message=Message(
+            role=Role.ROLE_USER,
+            message_id='msg_after_terminal_stream',
+            parts=[Part(text='Hi')],
+        )
+    )
+    with pytest.raises(
+        InvalidAgentResponseError, match='Message object in task mode'
+    ):
+        async for _ in request_handler.on_message_send_stream(
+            params, create_server_call_context()
+        ):
+            pass